Structure, evolution and phylogenetic informativeness of eelpouts (Cottoidei: Zoarcales) mitochondrial control region sequences.

Control region (CR) is a major non-coding domain of mitochondrial DNA in vertebrates which contains the promoters for replication and transcription of mitochondrial genome along with the binding sites for metabolic machinery and, hence, is a vital element for the integrity of mitochondrial genome as a biological replicator. The origin and diversity of structural elements within CR have been intensively studied in recent years with the involvement of new diverse taxa. In this paper, we provide new data on the nucleotide and structural patterns of CR evolution and phylogenetic suitability among eelpouts (Cottoidei: Zoarcales). To achieve this, we carried out a comparative phylogenetic and structural analysis of 29 CR sequences belonging to the long shanny Stichaeus grigorjewi together with nine sequences of other eelpouts taxa representing four families in contrast to mitochondrial protein-coding fragments. The CR organization within S. grigorjewi, as well as in all other eelpouts, is consistent with the common three-domain structure known from most vertebrates. We found a hidden CR variation constrains on the landscape level and a lack of nucleotide saturation. Finally, our results demonstrate the advantage of the length variation in CR sequences for phylogenetic reconstructions among eelpouts.